The present invention relates to a method and means for preparing foodstuffs or the like by means of boiling and/or steaming.
When boiling food in cooking vessels it is usually impossible to avoid deposits on the bottom and walls of the cooking vessel. In certain cases these deposits are extremely difficult to remove by cleaning. For this reason it is in many cases impossible to clean the cooking vessel in a satisfactory manner in a dishwasher, for instance, and it is only with difficulty that it can be cleaned manually. The deposits may also contain flavoring matter which adds to the difficulty of cleaning. As is known, thus, it is difficult to clean vessels which have been used for boiling potatoes, certain other vegetables, fish and so on. In the preparation of food containing fat such as sauces, purees, milk, a fat deposit is also obtained on the inner surface of the cooking vessel, which also makes cleaning difficult.
Attempts have been made to place an insert of disposable character in the cooking vessel, the insert--consisting of aluminum foil for example--being designed to be in contact with the inner wall and the bottom of the cooking vessel.
However, it has been found that for various reasons such an arrangement is not feasible. In the first place there is a considerable risk of water or other liquid remaining between the bottom of the vessel, for instance, and the insert. During heating this may result in violent expulsion of steam, so much so that even the contents of the vessel may be partially expelled. This is because the water between the bottom of the vessel and the insert is rapidly vaporized and expands. However, because of the pressure exerted by the insert from above, the steam is enclosed in a pocket resulting in strong over-pressure until the steam forces a path between the insert and the vessel.
The above arrangement is also unsuitable because it is difficult to find a heat-resistant material with good heattransfer properties. Good heat-resistance is necessary because extremely high temperatures may occur locally on the insert wall due to the direct contact between insert and cooking vessel. Even if aluminum foil is used for the insert, which in itself has good heat-resistance and good heat-conductivity, it is difficult to fit this to the shape of the cooking vessel so that no pockets of air, steam or water are formed between the vessel and the insert. This gives considerably reduced heat-conductivity and thus less economic heating. Furthermore, unless coated with plastic, for instance, aluminum foil is scarcely corrosion-resistant and is also sensitive to mechanical action. If a hole appears in the foil caused by corrosion or mechanically, liquid will leak out between cooking vessel and insert, resulting in the expulsion of air mentioned above. If, on the other hand, the foil is coated with plastic, it loses its heat resistance and the plastic may burn because of the high temperatures which may occur.
It has now been found that the difficulties and drawbacks mentioned above can be eliminated by means of the present invention.
In the method proposed according to the invention, the problem is solved substantially in that
the foodstuff to be cooked is placed in a disposable, liquid-tight film or foil insert, open at the top, and that
the disposable insert is spaced from the bottom and walls of a cooking vessel, possibly by means of a supporting holder surrounding the insert and allowing steam to pass through, so that a gap is formed and the foodstuff placed in the disposable insert is heated through the action of steam or water and steam in the gap.
According to a suitable embodiment of the invention the disposable insert is positioned in the cooking vessel by means of a supporting holder provided with steam passages. The combination of a thin insert of disposable type and a supporting holder surrounding the insert forms a unit during the cooking process. The supporting holder or casing is provided in suitable manner with passages for water vapor and water, for instance, in the form of perforations or by at least parts of the casing being made of stiffened mesh. The casing may thus consist of a wire basket. The unit formed by insert and casing should be designed so that when used for cooking in an ordinary cooking vessel, it is slightly smaller in height and diameter than the cooking vessel so that a space is obtained between the cooking vessel and the unit.
When preparing food by boiling, for instance, water is poured into the cooking vessel up to a suitable level. If the vessel is placed on a hot-plate the water in the bottom of the vessel will be brought to boil. Steam will be produced and at least some of this steam will condense on the outer surface of the insert, the heat being transmitted through the wall of the insert to the foodstuff. If the level of the water is sufficiently high in the cooking vessel for it to come into contact with the bottom of the unit, heat may also be conducted directly through the casing and the insert. Some of the steam produced by the boiling water may also be directed in suitable manner over the upper edge of the insert so that the steam condenses directly on the foodstuff.
If water or other liquid leaks through a hole in the insert into the space between the insert and cooking vessel, there is no risk of explosive puffs. Furthermore, the material need not be especially heat-resistant since the casing is separated from at least the bottom of the vessel and the temperature of the insert walls will not therefore exceed 100.degree. C. during cooking. Further features of the invention are revealed in the accompanying claims.